1. Field of the Invention
The present invention relates to honeycomb structure bodies made of promoter particles and inorganic binder particles and a method of producing the honeycomb structure bodies.
2. Description of the Related Art
There are known honeycomb structure bodies made of cordierite or SiC, etc., capable of purifying exhaust gas emitted from an internal combustion engine of a motor vehicle. Specifically, an exhaust gas purification catalyst is supported in the honeycomb structure body. That is, inorganic binder particles forming the honeycomb structure body support a promoter (or co-catalyst) made of ceria zirconia solid solution and noble metal catalyst.
Recently, there has been proposed a honeycomb structure body made of promoter components, etc. However, because it is difficult to perform the process of compacting and forming a solid mass of promoter particles together, i.e. the sintering of the promoter particles together, the produced honeycomb structure body has a weak strength when the honeycomb structure body contains such promoter particles. In order to solve such a conventional problem, there has been proposed a honeycomb structure body made of ceria particles, a ceramic material and inorganic binder particles. This ceramic material has a low self-sintering properties as compared with that of the ceria particles. For example, a patent document, Japanese patent No. 5185837 discloses such a honeycomb structure body.
By the way, it is requested to have an increased amount of components other than ceria particles in order for the honeycomb structure body to have an adequate strength. However, in this case, the properties of the promoter would cause a possible problem of deteriorating the exhaust gas purification performance. As a result, it is difficult for the honeycomb structure body to obtain the benefits of using the promoter particles.
On the other hand, increasing of the amount of the promoter particles would cause the honeycomb structure body to decrease in the necessary strength.